Observation of surface charging at the edge of a Schottky contact

Scanning Kelvin probe microscopy was used to detect reverse-bias-induced surface potential changes near the Schottky contact of a GaN Schottky diode. After application of a reverse bias, the surface potential near the Schottky contact gradually decreased with time, indicating an increase of band bending. Surface potential traces recorded after turning off the reverse bias indeed revealed increased band bending near the Schottky contact. A higher reverse bias caused a larger increase of band bending. The authors suggest that a reverse bias facilitates electron tunneling at the edge of the Schottky contact by decreasing the potential barrier width. Capture of these tunneled electrons by surface states causes the observed increase of band bending.